[rodh]

Wondering if someone could let me know if and where I can purchase an adapter to use canon lenses on my K3ii.

[Adam]

The short answer is that it isn't possible to adapt EOS lenses on Pentax DSLRs, more details here:

Canon Lens to Pentax Adapter/converter - PentaxForums.com

There is an adapter for FD lenses, however:

FotodioX Pro Lens Mount Adapter for Canon FD Lens to FD-PK-PRO

[richfam]

I bought one: a Fotodiox Pro Lens Mount Adapter - Canon FD & FL 35mm SLR lens to Pentax K (PK) Mount SLR Camera Body, but I can't recommend it except for macro work.

It does allow a Canon FD/FL lens to focus to infinity when mounted on a Pentax body, it does have a control ring to manually stop down the lens aperture, but it also acts as a 1.4x teleconverter (in addition to the 1.5x APS-C crop factor from your K-3ii body; it turns a 20mm ultra wide lens into the equivalent of a 42mm normal lens).

But...

There's only a single optical element, and the image quality is absolutely ghastly (good teleconverters often have 5 to 7 elements). I tried several of my Canon FD mount lenses with it, and the images were all fuzzy, low-contrast, soft-focus disasters.

You can remove the optical element and just use the adapter as a short extension tube for macro work, but without infinity focus. This is why I bought the adapter: I use it to mount a Vivitar 90mm f/2.8 macro lens in Canon FD mount to my Pentax K-70. It works really great for macro shots, but the maximum focus distance is about 5 ft. (with the lens set at infinity).

The optical element is easily removed if you have a spanner wrench; not so easily removed if you don't.

[UncleVanya]

Wondering if someone could let me know if and where I can purchase an adapter to use canon lenses on my K3ii.

There aren't any that are optically good.

In order to adapt a lens without adding corrective elements you need one with a longer flange focal distance than the native mount:
Flange focal distance - Wikipedia

Thus while Pentax K or Nikon F can be used without corrective optics on Canon FD/FL, EF, and RF, the Canon FD/FL and EF lenses can't be used without corrective optics on Nikon F mount cameras or Pentax K - but can be adapted without corrective optics to Nikon's Z mount cameras.

Adding a corrective teleconverter lens can allow use but generally the ones made are just terrible. Plus the lenses won't present a normal field of view as they are more telephoto than they were originally.

[Michail_P]

I’ve tried and currently use an adapter for my FD lenses and I only get ghastly images at very wide aperture values. Micro contrast is an issue but it can be easily fixed in pp.

[Wasp]

If you want to use Canon FD lenses on digital, the easy answer is to get a mirrorless camera and an adapter.

For example:

Vello Canon FD Lens to Sony E-Mount Camera Lens Adapter